dsh-project-brain: DSH Persistent Project Intelligence and Memory Plugin

`dsh-project-brain` is a plugin designed specifically for DeepSeek Harness to address the fragmentation of AI sessions and provide a persistent, structured local knowledge layer for software development projects. It automatically scans the workspace to generate architecture reports and persists decisions, historical records, and to-do items, enabling automatic context restoration in new sessions. The plugin supports a dual-fallback mechanism using local BM25 retrieval and AI generation, ensuring usability even without network access. It also provides export, import, and version rollback capabilities for the Project Brain, facilitating the migration of project state across different machines.